Computing devices can be used to request content from other computing devices over a communication network. In a common application, a client computing device can request a web page from a server computing device via the internet. Browser application software on the client computing device typically retrieves a requested web page, processes resource identifiers embedded in the web page to generate requests for additional resources (e.g., images, script files, etc.), and renders the content for presentation. From the perspective of a user of a client computing device, a user experience can be defined in terms of the performance and latencies associated with obtaining and rendering the requested network content on the client computing device. Latencies and performance limitations of any of the above processes may diminish the user experience.
Optimizations and other improvements may be implemented to reduce latency and otherwise improve the user experience. Conventionally, content providers or third parties may generate test requests (e.g., from a fleet of test devices or servers under the control of the content provider or a third party) in order to obtain performance data about the retrieval process for various content. This data may be analyzed to help identify the causes of latencies and performance limitations, and to implement optimizations and other improvements to the user experience.